One of the most important things to survive, other than oxygen, air pressure and other physical living conditions, is food. Given the technology currently available, it is possible to create a livable atmosphere on Mars in the form of closed spaces or spacesuits. Also, the energy to run operations can be harvested from the Sun in form of solar energy. This is only a one time setup, which if maintained properly can lead to the long-term survival of humans on Mars.
One of the important things to consider here is food and water, without which human life cannot exist. Availability of water on Mars has already been documented. The question remains about food. Even if we take food from earth, it will eventually be consumed. Making multiple trips to Mars solely to transport food is exorbitantly impractical, considering the money and time it takes to make a trip to Mars. The only method to have unlimited access to food at Mars growing food on Mars. Considering the climate and the soil conditions at Mars, we may not have a wide variety of things we can grow there. However, basic food like potatoes and vegetables can still be grown, which are enough for human survival¹.
One of the things to be noted is that the soil at Mars is toxic and to grow anything on it, we will first have to decontaminate it by removing some harsh chemicals from the soil, which is possible to do on Mars itself². NASA’s experience in hydroponics may be a help.
If all these experiments work, then not only humans, but animals can also be taken to Mars for meat and dairy products and they can be kept in closed spaces where no spacesuit is required. Although it is a long term process which requires a lot of money, technology, manpower and willing people who want to go there, it is possible to see people living on Mars without trouble, just as they live on Earth now, in the next 100 years.
Figure 3³
The picture above is the concept of what a habitat for humans will look like on Mars. Part of the habitat will be under soil to protect us from radiation from space while agricultural spaces will require the Sun for growth 4. Equipment and space vehicles are shown throughout the outside of the habitat.
¹ Williams, M. (2016, October 3). HOW CAN WE LIVE ON MARS?.
Retrieved December 2, 2016 from
http://www.universetoday.com/111462/how-can-we-live-on-mars/
² Williams.
³ Williams.
4 Williams.